The invention relates to a heating pad adapted for use in an environment where the pad can be expected to be exposed to moisture and rough conditions or handling. For example, such heating pads are useful in a greenhouse as a bench pad to be placed under pots or other growing containers. Such greenhouse heating pads typically have incorporated a heating element embedded within a rubber or polymeric material, manufactured in a process that involves the application of heat in order to effect the desired bond and seal between the components of the heating pad. The use of heat and materials that require application of heat in the manufacturing process necessarily complicates the process and adds to the cost of manufacture. In addition to the relatively high cost of heat sealable polymeric materials and the energy to effect their seal, the heat developed during the sealing process may distort or otherwise effect the operating characteristics of the electrical resistance heating element which may have an operating temperature range less than that required to effect the heat sealing process.
It would be desirable to provide a water resistant heater pad having an embedded heating element that is capable of manufacture in a simple, low-cost process, yet which is durable and is adapted for rough use.